The purpose of this research study is to gather information from people diagnosed with IBS to compare alosetron to placebo for differences in your general health, physical and mental health, work absences, and productivity, and to measure the impact of IBS on your lifestyle over a one year period. A second purpose of this research study is to assess the long term use of alosetron by monitoring changes in laboratory tests, hearing, heart function, and any changes in your overall health over a one-year period.